jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp@b9bc732be7c0 (annotated)

src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp@b9bc732be7c0 (annotated)

src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp

Thu, 10 Jun 2010 08:27:35 -0700

author: jmasa
date: Thu, 10 Jun 2010 08:27:35 -0700
changeset 1949: b9bc732be7c0
parent 1907: c18cbe5936b8
child 1966: 215576b54709
permissions: -rw-r--r--

Merge

 /*
  * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */
 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
 // It uses the "Garbage First" heap organization and algorithm, which
 // may combine concurrent marking with parallel, incremental compaction of
 // heap subsets that will yield large amounts of garbage.
 class HeapRegion;
 class HeapRegionSeq;
 class PermanentGenerationSpec;
 class GenerationSpec;
 class OopsInHeapRegionClosure;
 class G1ScanHeapEvacClosure;
 class ObjectClosure;
 class SpaceClosure;
 class CompactibleSpaceClosure;
 class Space;
 class G1CollectorPolicy;
 class GenRemSet;
 class G1RemSet;
 class HeapRegionRemSetIterator;
 class ConcurrentMark;
 class ConcurrentMarkThread;
 class ConcurrentG1Refine;
 class ConcurrentZFThread;
 // If want to accumulate detailed statistics on work queues
 // turn this on.
 #define G1_DETAILED_STATS 0
 #if G1_DETAILED_STATS
 #  define IF_G1_DETAILED_STATS(code) code
 #else
 #  define IF_G1_DETAILED_STATS(code)
 #endif
 typedef GenericTaskQueue<StarTask>          RefToScanQueue;
 typedef GenericTaskQueueSet<RefToScanQueue> RefToScanQueueSet;
 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
 enum G1GCThreadGroups {
   G1CRGroup = 0,
   G1ZFGroup = 1,
   G1CMGroup = 2,
   G1CLGroup = 3
 };
 enum GCAllocPurpose {
   GCAllocForTenured,
   GCAllocForSurvived,
   GCAllocPurposeCount
 };
 class YoungList : public CHeapObj {
 private:
   G1CollectedHeap* _g1h;
   HeapRegion* _head;
   HeapRegion* _survivor_head;
   HeapRegion* _survivor_tail;
   HeapRegion* _curr;
   size_t      _length;
   size_t      _survivor_length;
   size_t      _last_sampled_rs_lengths;
   size_t      _sampled_rs_lengths;
   void         empty_list(HeapRegion* list);
 public:
   YoungList(G1CollectedHeap* g1h);
   void         push_region(HeapRegion* hr);
   void         add_survivor_region(HeapRegion* hr);
   void         empty_list();
   bool         is_empty() { return _length == 0; }
   size_t       length() { return _length; }
   size_t       survivor_length() { return _survivor_length; }
   void rs_length_sampling_init();
   bool rs_length_sampling_more();
   void rs_length_sampling_next();
   void reset_sampled_info() {
     _last_sampled_rs_lengths =   0;
   }
   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
   // for development purposes
   void reset_auxilary_lists();
   void clear() { _head = NULL; _length = 0; }
   void clear_survivors() {
     _survivor_head    = NULL;
     _survivor_tail    = NULL;
     _survivor_length  = 0;
   }
   HeapRegion* first_region() { return _head; }
   HeapRegion* first_survivor_region() { return _survivor_head; }
   HeapRegion* last_survivor_region() { return _survivor_tail; }
   // debugging
   bool          check_list_well_formed();
   bool          check_list_empty(bool check_sample = true);
   void          print();
 };
 class RefineCardTableEntryClosure;
 class G1CollectedHeap : public SharedHeap {
   friend class VM_G1CollectForAllocation;
   friend class VM_GenCollectForPermanentAllocation;
   friend class VM_G1CollectFull;
   friend class VM_G1IncCollectionPause;
   friend class VMStructs;
   // Closures used in implementation.
   friend class G1ParCopyHelper;
   friend class G1IsAliveClosure;
   friend class G1EvacuateFollowersClosure;
   friend class G1ParScanThreadState;
   friend class G1ParScanClosureSuper;
   friend class G1ParEvacuateFollowersClosure;
   friend class G1ParTask;
   friend class G1FreeGarbageRegionClosure;
   friend class RefineCardTableEntryClosure;
   friend class G1PrepareCompactClosure;
   friend class RegionSorter;
   friend class CountRCClosure;
   friend class EvacPopObjClosure;
   friend class G1ParCleanupCTTask;
   // Other related classes.
   friend class G1MarkSweep;
 private:
   // The one and only G1CollectedHeap, so static functions can find it.
   static G1CollectedHeap* _g1h;
   static size_t _humongous_object_threshold_in_words;
   // Storage for the G1 heap (excludes the permanent generation).
   VirtualSpace _g1_storage;
   MemRegion    _g1_reserved;
   // The part of _g1_storage that is currently committed.
   MemRegion _g1_committed;
   // The maximum part of _g1_storage that has ever been committed.
   MemRegion _g1_max_committed;
   // The number of regions that are completely free.
   size_t _free_regions;
   // The number of regions we could create by expansion.
   size_t _expansion_regions;
   // Return the number of free regions in the heap (by direct counting.)
   size_t count_free_regions();
   // Return the number of free regions on the free and unclean lists.
   size_t count_free_regions_list();
   // The block offset table for the G1 heap.
   G1BlockOffsetSharedArray* _bot_shared;
   // Move all of the regions off the free lists, then rebuild those free
   // lists, before and after full GC.
   void tear_down_region_lists();
   void rebuild_region_lists();
   // This sets all non-empty regions to need zero-fill (which they will if
   // they are empty after full collection.)
   void set_used_regions_to_need_zero_fill();
   // The sequence of all heap regions in the heap.
   HeapRegionSeq* _hrs;
   // The region from which normal-sized objects are currently being
   // allocated.  May be NULL.
   HeapRegion* _cur_alloc_region;
   // Postcondition: cur_alloc_region == NULL.
   void abandon_cur_alloc_region();
   void abandon_gc_alloc_regions();
   // The to-space memory regions into which objects are being copied during
   // a GC.
   HeapRegion* _gc_alloc_regions[GCAllocPurposeCount];
   size_t _gc_alloc_region_counts[GCAllocPurposeCount];
   // These are the regions, one per GCAllocPurpose, that are half-full
   // at the end of a collection and that we want to reuse during the
   // next collection.
   HeapRegion* _retained_gc_alloc_regions[GCAllocPurposeCount];
   // This specifies whether we will keep the last half-full region at
   // the end of a collection so that it can be reused during the next
   // collection (this is specified per GCAllocPurpose)
   bool _retain_gc_alloc_region[GCAllocPurposeCount];
   // A list of the regions that have been set to be alloc regions in the
   // current collection.
   HeapRegion* _gc_alloc_region_list;
   // Determines PLAB size for a particular allocation purpose.
   static size_t desired_plab_sz(GCAllocPurpose purpose);
   // When called by par thread, require par_alloc_during_gc_lock() to be held.
   void push_gc_alloc_region(HeapRegion* hr);
   // This should only be called single-threaded.  Undeclares all GC alloc
   // regions.
   void forget_alloc_region_list();
   // Should be used to set an alloc region, because there's other
   // associated bookkeeping.
   void set_gc_alloc_region(int purpose, HeapRegion* r);
   // Check well-formedness of alloc region list.
   bool check_gc_alloc_regions();
   // Outside of GC pauses, the number of bytes used in all regions other
   // than the current allocation region.
   size_t _summary_bytes_used;
   // This is used for a quick test on whether a reference points into
   // the collection set or not. Basically, we have an array, with one
   // byte per region, and that byte denotes whether the corresponding
   // region is in the collection set or not. The entry corresponding
   // the bottom of the heap, i.e., region 0, is pointed to by
   // _in_cset_fast_test_base.  The _in_cset_fast_test field has been
   // biased so that it actually points to address 0 of the address
   // space, to make the test as fast as possible (we can simply shift
   // the address to address into it, instead of having to subtract the
   // bottom of the heap from the address before shifting it; basically
   // it works in the same way the card table works).
   bool* _in_cset_fast_test;
   // The allocated array used for the fast test on whether a reference
   // points into the collection set or not. This field is also used to
   // free the array.
   bool* _in_cset_fast_test_base;
   // The length of the _in_cset_fast_test_base array.
   size_t _in_cset_fast_test_length;
   volatile unsigned _gc_time_stamp;
   size_t* _surviving_young_words;
   void setup_surviving_young_words();
   void update_surviving_young_words(size_t* surv_young_words);
   void cleanup_surviving_young_words();
 protected:
   // Returns "true" iff none of the gc alloc regions have any allocations
   // since the last call to "save_marks".
   bool all_alloc_regions_no_allocs_since_save_marks();
   // Perform finalization stuff on all allocation regions.
   void retire_all_alloc_regions();
   // The number of regions allocated to hold humongous objects.
   int         _num_humongous_regions;
   YoungList*  _young_list;
   // The current policy object for the collector.
   G1CollectorPolicy* _g1_policy;
   // Parallel allocation lock to protect the current allocation region.
   Mutex  _par_alloc_during_gc_lock;
   Mutex* par_alloc_during_gc_lock() { return &_par_alloc_during_gc_lock; }
   // If possible/desirable, allocate a new HeapRegion for normal object
   // allocation sufficient for an allocation of the given "word_size".
   // If "do_expand" is true, will attempt to expand the heap if necessary
   // to to satisfy the request.  If "zero_filled" is true, requires a
   // zero-filled region.
   // (Returning NULL will trigger a GC.)
   virtual HeapRegion* newAllocRegion_work(size_t word_size,
                                           bool do_expand,
                                           bool zero_filled);
   virtual HeapRegion* newAllocRegion(size_t word_size,
                                      bool zero_filled = true) {
     return newAllocRegion_work(word_size, false, zero_filled);
   }
   virtual HeapRegion* newAllocRegionWithExpansion(int purpose,
                                                   size_t word_size,
                                                   bool zero_filled = true);
   // Attempt to allocate an object of the given (very large) "word_size".
   // Returns "NULL" on failure.
   virtual HeapWord* humongousObjAllocate(size_t word_size);
   // If possible, allocate a block of the given word_size, else return "NULL".
   // Returning NULL will trigger GC or heap expansion.
   // These two methods have rather awkward pre- and
   // post-conditions. If they are called outside a safepoint, then
   // they assume that the caller is holding the heap lock. Upon return
   // they release the heap lock, if they are returning a non-NULL
   // value. attempt_allocation_slow() also dirties the cards of a
   // newly-allocated young region after it releases the heap
   // lock. This change in interface was the neatest way to achieve
   // this card dirtying without affecting mem_allocate(), which is a
   // more frequently called method. We tried two or three different
   // approaches, but they were even more hacky.
   HeapWord* attempt_allocation(size_t word_size,
                                bool permit_collection_pause = true);
   HeapWord* attempt_allocation_slow(size_t word_size,
                                     bool permit_collection_pause = true);
   // Allocate blocks during garbage collection. Will ensure an
   // allocation region, either by picking one or expanding the
   // heap, and then allocate a block of the given size. The block
   // may not be a humongous - it must fit into a single heap region.
   HeapWord* allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
   HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
   HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
                                     HeapRegion*    alloc_region,
                                     bool           par,
                                     size_t         word_size);
   // Ensure that no further allocations can happen in "r", bearing in mind
   // that parallel threads might be attempting allocations.
   void par_allocate_remaining_space(HeapRegion* r);
   // Retires an allocation region when it is full or at the end of a
   // GC pause.
   void  retire_alloc_region(HeapRegion* alloc_region, bool par);
   // Helper function for two callbacks below.
   // "full", if true, indicates that the GC is for a System.gc() request,
   // and should collect the entire heap.  If "clear_all_soft_refs" is true,
   // all soft references are cleared during the GC.  If "full" is false,
   // "word_size" describes the allocation that the GC should
   // attempt (at least) to satisfy.
   void do_collection(bool full, bool clear_all_soft_refs,
                      size_t word_size);
   // Callback from VM_G1CollectFull operation.
   // Perform a full collection.
   void do_full_collection(bool clear_all_soft_refs);
   // Resize the heap if necessary after a full collection.  If this is
   // after a collect-for allocation, "word_size" is the allocation size,
   // and will be considered part of the used portion of the heap.
   void resize_if_necessary_after_full_collection(size_t word_size);
   // Callback from VM_G1CollectForAllocation operation.
   // This function does everything necessary/possible to satisfy a
   // failed allocation request (including collection, expansion, etc.)
   HeapWord* satisfy_failed_allocation(size_t word_size);
   // Attempting to expand the heap sufficiently
   // to support an allocation of the given "word_size".  If
   // successful, perform the allocation and return the address of the
   // allocated block, or else "NULL".
   virtual HeapWord* expand_and_allocate(size_t word_size);
 public:
   // Expand the garbage-first heap by at least the given size (in bytes!).
   // (Rounds up to a HeapRegion boundary.)
   virtual void expand(size_t expand_bytes);
   // Do anything common to GC's.
   virtual void gc_prologue(bool full);
   virtual void gc_epilogue(bool full);
   // We register a region with the fast "in collection set" test. We
   // simply set to true the array slot corresponding to this region.
   void register_region_with_in_cset_fast_test(HeapRegion* r) {
     assert(_in_cset_fast_test_base != NULL, "sanity");
     assert(r->in_collection_set(), "invariant");
     int index = r->hrs_index();
     assert(0 <= index && (size_t) index < _in_cset_fast_test_length, "invariant");
     assert(!_in_cset_fast_test_base[index], "invariant");
     _in_cset_fast_test_base[index] = true;
   }
   // This is a fast test on whether a reference points into the
   // collection set or not. It does not assume that the reference
   // points into the heap; if it doesn't, it will return false.
   bool in_cset_fast_test(oop obj) {
     assert(_in_cset_fast_test != NULL, "sanity");
     if (_g1_committed.contains((HeapWord*) obj)) {
       // no need to subtract the bottom of the heap from obj,
       // _in_cset_fast_test is biased
       size_t index = ((size_t) obj) >> HeapRegion::LogOfHRGrainBytes;
       bool ret = _in_cset_fast_test[index];
       // let's make sure the result is consistent with what the slower
       // test returns
       assert( ret || !obj_in_cs(obj), "sanity");
       assert(!ret ||  obj_in_cs(obj), "sanity");
       return ret;
     } else {
       return false;
     }
   }
   void clear_cset_fast_test() {
     assert(_in_cset_fast_test_base != NULL, "sanity");
     memset(_in_cset_fast_test_base, false,
         _in_cset_fast_test_length * sizeof(bool));
   }
 protected:
   // Shrink the garbage-first heap by at most the given size (in bytes!).
   // (Rounds down to a HeapRegion boundary.)
   virtual void shrink(size_t expand_bytes);
   void shrink_helper(size_t expand_bytes);
   // Do an incremental collection: identify a collection set, and evacuate
   // its live objects elsewhere.
   virtual void do_collection_pause();
   // The guts of the incremental collection pause, executed by the vm
   // thread.
   virtual void do_collection_pause_at_safepoint();
   // Actually do the work of evacuating the collection set.
   virtual void evacuate_collection_set();
   // If this is an appropriate right time, do a collection pause.
   // The "word_size" argument, if non-zero, indicates the size of an
   // allocation request that is prompting this query.
   void do_collection_pause_if_appropriate(size_t word_size);
   // The g1 remembered set of the heap.
   G1RemSet* _g1_rem_set;
   // And it's mod ref barrier set, used to track updates for the above.
   ModRefBarrierSet* _mr_bs;
   // A set of cards that cover the objects for which the Rsets should be updated
   // concurrently after the collection.
   DirtyCardQueueSet _dirty_card_queue_set;
   // The Heap Region Rem Set Iterator.
   HeapRegionRemSetIterator** _rem_set_iterator;
   // The closure used to refine a single card.
   RefineCardTableEntryClosure* _refine_cte_cl;
   // A function to check the consistency of dirty card logs.
   void check_ct_logs_at_safepoint();
   // After a collection pause, make the regions in the CS into free
   // regions.
   void free_collection_set(HeapRegion* cs_head);
   // Abandon the current collection set without recording policy
   // statistics or updating free lists.
   void abandon_collection_set(HeapRegion* cs_head);
   // Applies "scan_non_heap_roots" to roots outside the heap,
   // "scan_rs" to roots inside the heap (having done "set_region" to
   // indicate the region in which the root resides), and does "scan_perm"
   // (setting the generation to the perm generation.)  If "scan_rs" is
   // NULL, then this step is skipped.  The "worker_i"
   // param is for use with parallel roots processing, and should be
   // the "i" of the calling parallel worker thread's work(i) function.
   // In the sequential case this param will be ignored.
   void g1_process_strong_roots(bool collecting_perm_gen,
                                SharedHeap::ScanningOption so,
                                OopClosure* scan_non_heap_roots,
                                OopsInHeapRegionClosure* scan_rs,
                                OopsInGenClosure* scan_perm,
                                int worker_i);
   // Apply "blk" to all the weak roots of the system.  These include
   // JNI weak roots, the code cache, system dictionary, symbol table,
   // string table, and referents of reachable weak refs.
   void g1_process_weak_roots(OopClosure* root_closure,
                              OopClosure* non_root_closure);
   // Invoke "save_marks" on all heap regions.
   void save_marks();
   // Free a heap region.
   void free_region(HeapRegion* hr);
   // A component of "free_region", exposed for 'batching'.
   // All the params after "hr" are out params: the used bytes of the freed
   // region(s), the number of H regions cleared, the number of regions
   // freed, and pointers to the head and tail of a list of freed contig
   // regions, linked throught the "next_on_unclean_list" field.
   void free_region_work(HeapRegion* hr,
                         size_t& pre_used,
                         size_t& cleared_h,
                         size_t& freed_regions,
                         UncleanRegionList* list,
                         bool par = false);
   // The concurrent marker (and the thread it runs in.)
   ConcurrentMark* _cm;
   ConcurrentMarkThread* _cmThread;
   bool _mark_in_progress;
   // The concurrent refiner.
   ConcurrentG1Refine* _cg1r;
   // The concurrent zero-fill thread.
   ConcurrentZFThread* _czft;
   // The parallel task queues
   RefToScanQueueSet *_task_queues;
   // True iff a evacuation has failed in the current collection.
   bool _evacuation_failed;
   // Set the attribute indicating whether evacuation has failed in the
   // current collection.
   void set_evacuation_failed(bool b) { _evacuation_failed = b; }
   // Failed evacuations cause some logical from-space objects to have
   // forwarding pointers to themselves.  Reset them.
   void remove_self_forwarding_pointers();
   // When one is non-null, so is the other.  Together, they each pair is
   // an object with a preserved mark, and its mark value.
   GrowableArray<oop>*     _objs_with_preserved_marks;
   GrowableArray<markOop>* _preserved_marks_of_objs;
   // Preserve the mark of "obj", if necessary, in preparation for its mark
   // word being overwritten with a self-forwarding-pointer.
   void preserve_mark_if_necessary(oop obj, markOop m);
   // The stack of evac-failure objects left to be scanned.
   GrowableArray<oop>*    _evac_failure_scan_stack;
   // The closure to apply to evac-failure objects.
   OopsInHeapRegionClosure* _evac_failure_closure;
   // Set the field above.
   void
   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
     _evac_failure_closure = evac_failure_closure;
   }
   // Push "obj" on the scan stack.
   void push_on_evac_failure_scan_stack(oop obj);
   // Process scan stack entries until the stack is empty.
   void drain_evac_failure_scan_stack();
   // True iff an invocation of "drain_scan_stack" is in progress; to
   // prevent unnecessary recursion.
   bool _drain_in_progress;
   // Do any necessary initialization for evacuation-failure handling.
   // "cl" is the closure that will be used to process evac-failure
   // objects.
   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
   // Do any necessary cleanup for evacuation-failure handling data
   // structures.
   void finalize_for_evac_failure();
   // An attempt to evacuate "obj" has failed; take necessary steps.
   void handle_evacuation_failure(oop obj);
   oop handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop obj);
   void handle_evacuation_failure_common(oop obj, markOop m);
   // Ensure that the relevant gc_alloc regions are set.
   void get_gc_alloc_regions();
   // We're done with GC alloc regions. We are going to tear down the
   // gc alloc list and remove the gc alloc tag from all the regions on
   // that list. However, we will also retain the last (i.e., the one
   // that is half-full) GC alloc region, per GCAllocPurpose, for
   // possible reuse during the next collection, provided
   // _retain_gc_alloc_region[] indicates that it should be the
   // case. Said regions are kept in the _retained_gc_alloc_regions[]
   // array. If the parameter totally is set, we will not retain any
   // regions, irrespective of what _retain_gc_alloc_region[]
   // indicates.
   void release_gc_alloc_regions(bool totally);
 #ifndef PRODUCT
   // Useful for debugging.
   void print_gc_alloc_regions();
 #endif // !PRODUCT
   // ("Weak") Reference processing support
   ReferenceProcessor* _ref_processor;
   enum G1H_process_strong_roots_tasks {
     G1H_PS_mark_stack_oops_do,
     G1H_PS_refProcessor_oops_do,
     // Leave this one last.
     G1H_PS_NumElements
   };
   SubTasksDone* _process_strong_tasks;
   // List of regions which require zero filling.
   UncleanRegionList _unclean_region_list;
   bool _unclean_regions_coming;
 public:
   void set_refine_cte_cl_concurrency(bool concurrent);
   RefToScanQueue *task_queue(int i);
   // A set of cards where updates happened during the GC
   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
   // Create a G1CollectedHeap with the specified policy.
   // Must call the initialize method afterwards.
   // May not return if something goes wrong.
   G1CollectedHeap(G1CollectorPolicy* policy);
   // Initialize the G1CollectedHeap to have the initial and
   // maximum sizes, permanent generation, and remembered and barrier sets
   // specified by the policy object.
   jint initialize();
   void ref_processing_init();
   void set_par_threads(int t) {
     SharedHeap::set_par_threads(t);
     _process_strong_tasks->set_par_threads(t);
   }
   virtual CollectedHeap::Name kind() const {
     return CollectedHeap::G1CollectedHeap;
   }
   // The current policy object for the collector.
   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
   // Adaptive size policy.  No such thing for g1.
   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
   // The rem set and barrier set.
   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
   ModRefBarrierSet* mr_bs() const { return _mr_bs; }
   // The rem set iterator.
   HeapRegionRemSetIterator* rem_set_iterator(int i) {
     return _rem_set_iterator[i];
   }
   HeapRegionRemSetIterator* rem_set_iterator() {
     return _rem_set_iterator[0];
   }
   unsigned get_gc_time_stamp() {
     return _gc_time_stamp;
   }
   void reset_gc_time_stamp() {
     _gc_time_stamp = 0;
     OrderAccess::fence();
   }
   void increment_gc_time_stamp() {
     ++_gc_time_stamp;
     OrderAccess::fence();
   }
   void iterate_dirty_card_closure(bool concurrent, int worker_i);
   // The shared block offset table array.
   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
   // Reference Processing accessor
   ReferenceProcessor* ref_processor() { return _ref_processor; }
   // Reserved (g1 only; super method includes perm), capacity and the used
   // portion in bytes.
   size_t g1_reserved_obj_bytes() const { return _g1_reserved.byte_size(); }
   virtual size_t capacity() const;
   virtual size_t used() const;
   // This should be called when we're not holding the heap lock. The
   // result might be a bit inaccurate.
   size_t used_unlocked() const;
   size_t recalculate_used() const;
 #ifndef PRODUCT
   size_t recalculate_used_regions() const;
 #endif // PRODUCT
   // These virtual functions do the actual allocation.
   virtual HeapWord* mem_allocate(size_t word_size,
                                  bool   is_noref,
                                  bool   is_tlab,
                                  bool* gc_overhead_limit_was_exceeded);
   // Some heaps may offer a contiguous region for shared non-blocking
   // allocation, via inlined code (by exporting the address of the top and
   // end fields defining the extent of the contiguous allocation region.)
   // But G1CollectedHeap doesn't yet support this.
   // Return an estimate of the maximum allocation that could be performed
   // without triggering any collection or expansion activity.  In a
   // generational collector, for example, this is probably the largest
   // allocation that could be supported (without expansion) in the youngest
   // generation.  It is "unsafe" because no locks are taken; the result
   // should be treated as an approximation, not a guarantee, for use in
   // heuristic resizing decisions.
   virtual size_t unsafe_max_alloc();
   virtual bool is_maximal_no_gc() const {
     return _g1_storage.uncommitted_size() == 0;
   }
   // The total number of regions in the heap.
   size_t n_regions();
   // The number of regions that are completely free.
   size_t max_regions();
   // The number of regions that are completely free.
   size_t free_regions();
   // The number of regions that are not completely free.
   size_t used_regions() { return n_regions() - free_regions(); }
   // True iff the ZF thread should run.
   bool should_zf();
   // The number of regions available for "regular" expansion.
   size_t expansion_regions() { return _expansion_regions; }
 #ifndef PRODUCT
   bool regions_accounted_for();
   bool print_region_accounting_info();
   void print_region_counts();
 #endif
   HeapRegion* alloc_region_from_unclean_list(bool zero_filled);
   HeapRegion* alloc_region_from_unclean_list_locked(bool zero_filled);
   void put_region_on_unclean_list(HeapRegion* r);
   void put_region_on_unclean_list_locked(HeapRegion* r);
   void prepend_region_list_on_unclean_list(UncleanRegionList* list);
   void prepend_region_list_on_unclean_list_locked(UncleanRegionList* list);
   void set_unclean_regions_coming(bool b);
   void set_unclean_regions_coming_locked(bool b);
   // Wait for cleanup to be complete.
   void wait_for_cleanup_complete();
   // Like above, but assumes that the calling thread owns the Heap_lock.
   void wait_for_cleanup_complete_locked();
   // Return the head of the unclean list.
   HeapRegion* peek_unclean_region_list_locked();
   // Remove and return the head of the unclean list.
   HeapRegion* pop_unclean_region_list_locked();
   // List of regions which are zero filled and ready for allocation.
   HeapRegion* _free_region_list;
   // Number of elements on the free list.
   size_t _free_region_list_size;
   // If the head of the unclean list is ZeroFilled, move it to the free
   // list.
   bool move_cleaned_region_to_free_list_locked();
   bool move_cleaned_region_to_free_list();
   void put_free_region_on_list_locked(HeapRegion* r);
   void put_free_region_on_list(HeapRegion* r);
   // Remove and return the head element of the free list.
   HeapRegion* pop_free_region_list_locked();
   // If "zero_filled" is true, we first try the free list, then we try the
   // unclean list, zero-filling the result.  If "zero_filled" is false, we
   // first try the unclean list, then the zero-filled list.
   HeapRegion* alloc_free_region_from_lists(bool zero_filled);
   // Verify the integrity of the region lists.
   void remove_allocated_regions_from_lists();
   bool verify_region_lists();
   bool verify_region_lists_locked();
   size_t unclean_region_list_length();
   size_t free_region_list_length();
   // Perform a collection of the heap; intended for use in implementing
   // "System.gc".  This probably implies as full a collection as the
   // "CollectedHeap" supports.
   virtual void collect(GCCause::Cause cause);
   // The same as above but assume that the caller holds the Heap_lock.
   void collect_locked(GCCause::Cause cause);
   // This interface assumes that it's being called by the
   // vm thread. It collects the heap assuming that the
   // heap lock is already held and that we are executing in
   // the context of the vm thread.
   virtual void collect_as_vm_thread(GCCause::Cause cause);
   // True iff a evacuation has failed in the most-recent collection.
   bool evacuation_failed() { return _evacuation_failed; }
   // Free a region if it is totally full of garbage.  Returns the number of
   // bytes freed (0 ==> didn't free it).
   size_t free_region_if_totally_empty(HeapRegion *hr);
   void free_region_if_totally_empty_work(HeapRegion *hr,
                                          size_t& pre_used,
                                          size_t& cleared_h_regions,
                                          size_t& freed_regions,
                                          UncleanRegionList* list,
                                          bool par = false);
   // If we've done free region work that yields the given changes, update
   // the relevant global variables.
   void finish_free_region_work(size_t pre_used,
                                size_t cleared_h_regions,
                                size_t freed_regions,
                                UncleanRegionList* list);
   // Returns "TRUE" iff "p" points into the allocated area of the heap.
   virtual bool is_in(const void* p) const;
   // Return "TRUE" iff the given object address is within the collection
   // set.
   inline bool obj_in_cs(oop obj);
   // Return "TRUE" iff the given object address is in the reserved
   // region of g1 (excluding the permanent generation).
   bool is_in_g1_reserved(const void* p) const {
     return _g1_reserved.contains(p);
   }
   // Returns a MemRegion that corresponds to the space that  has been
   // committed in the heap
   MemRegion g1_committed() {
     return _g1_committed;
   }
   NOT_PRODUCT(bool is_in_closed_subset(const void* p) const;)
   // Dirty card table entries covering a list of young regions.
   void dirtyCardsForYoungRegions(CardTableModRefBS* ct_bs, HeapRegion* list);
   // This resets the card table to all zeros.  It is used after
   // a collection pause which used the card table to claim cards.
   void cleanUpCardTable();
   // Iteration functions.
   // Iterate over all the ref-containing fields of all objects, calling
   // "cl.do_oop" on each.
   virtual void oop_iterate(OopClosure* cl) {
     oop_iterate(cl, true);
   }
   void oop_iterate(OopClosure* cl, bool do_perm);
   // Same as above, restricted to a memory region.
   virtual void oop_iterate(MemRegion mr, OopClosure* cl) {
     oop_iterate(mr, cl, true);
   }
   void oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm);
   // Iterate over all objects, calling "cl.do_object" on each.
   virtual void object_iterate(ObjectClosure* cl) {
     object_iterate(cl, true);
   }
   virtual void safe_object_iterate(ObjectClosure* cl) {
     object_iterate(cl, true);
   }
   void object_iterate(ObjectClosure* cl, bool do_perm);
   // Iterate over all objects allocated since the last collection, calling
   // "cl.do_object" on each.  The heap must have been initialized properly
   // to support this function, or else this call will fail.
   virtual void object_iterate_since_last_GC(ObjectClosure* cl);
   // Iterate over all spaces in use in the heap, in ascending address order.
   virtual void space_iterate(SpaceClosure* cl);
   // Iterate over heap regions, in address order, terminating the
   // iteration early if the "doHeapRegion" method returns "true".
   void heap_region_iterate(HeapRegionClosure* blk);
   // Iterate over heap regions starting with r (or the first region if "r"
   // is NULL), in address order, terminating early if the "doHeapRegion"
   // method returns "true".
   void heap_region_iterate_from(HeapRegion* r, HeapRegionClosure* blk);
   // As above but starting from the region at index idx.
   void heap_region_iterate_from(int idx, HeapRegionClosure* blk);
   HeapRegion* region_at(size_t idx);
   // Divide the heap region sequence into "chunks" of some size (the number
   // of regions divided by the number of parallel threads times some
   // overpartition factor, currently 4).  Assumes that this will be called
   // in parallel by ParallelGCThreads worker threads with discinct worker
   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
   // calls will use the same "claim_value", and that that claim value is
   // different from the claim_value of any heap region before the start of
   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
   // attempting to claim the first region in each chunk, and, if
   // successful, applying the closure to each region in the chunk (and
   // setting the claim value of the second and subsequent regions of the
   // chunk.)  For now requires that "doHeapRegion" always returns "false",
   // i.e., that a closure never attempt to abort a traversal.
   void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
                                        int worker,
                                        jint claim_value);
   // It resets all the region claim values to the default.
   void reset_heap_region_claim_values();
 #ifdef ASSERT
   bool check_heap_region_claim_values(jint claim_value);
 #endif // ASSERT
   // Iterate over the regions (if any) in the current collection set.
   void collection_set_iterate(HeapRegionClosure* blk);
   // As above but starting from region r
   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
   // Returns the first (lowest address) compactible space in the heap.
   virtual CompactibleSpace* first_compactible_space();
   // A CollectedHeap will contain some number of spaces.  This finds the
   // space containing a given address, or else returns NULL.
   virtual Space* space_containing(const void* addr) const;
   // A G1CollectedHeap will contain some number of heap regions.  This
   // finds the region containing a given address, or else returns NULL.
   HeapRegion* heap_region_containing(const void* addr) const;
   // Like the above, but requires "addr" to be in the heap (to avoid a
   // null-check), and unlike the above, may return an continuing humongous
   // region.
   HeapRegion* heap_region_containing_raw(const void* addr) const;
   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
   // each address in the (reserved) heap is a member of exactly
   // one block.  The defining characteristic of a block is that it is
   // possible to find its size, and thus to progress forward to the next
   // block.  (Blocks may be of different sizes.)  Thus, blocks may
   // represent Java objects, or they might be free blocks in a
   // free-list-based heap (or subheap), as long as the two kinds are
   // distinguishable and the size of each is determinable.
   // Returns the address of the start of the "block" that contains the
   // address "addr".  We say "blocks" instead of "object" since some heaps
   // may not pack objects densely; a chunk may either be an object or a
   // non-object.
   virtual HeapWord* block_start(const void* addr) const;
   // Requires "addr" to be the start of a chunk, and returns its size.
   // "addr + size" is required to be the start of a new chunk, or the end
   // of the active area of the heap.
   virtual size_t block_size(const HeapWord* addr) const;
   // Requires "addr" to be the start of a block, and returns "TRUE" iff
   // the block is an object.
   virtual bool block_is_obj(const HeapWord* addr) const;
   // Does this heap support heap inspection? (+PrintClassHistogram)
   virtual bool supports_heap_inspection() const { return true; }
   // Section on thread-local allocation buffers (TLABs)
   // See CollectedHeap for semantics.
   virtual bool supports_tlab_allocation() const;
   virtual size_t tlab_capacity(Thread* thr) const;
   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
   virtual HeapWord* allocate_new_tlab(size_t size);
   // Can a compiler initialize a new object without store barriers?
   // This permission only extends from the creation of a new object
   // via a TLAB up to the first subsequent safepoint. If such permission
   // is granted for this heap type, the compiler promises to call
   // defer_store_barrier() below on any slow path allocation of
   // a new object for which such initializing store barriers will
   // have been elided. G1, like CMS, allows this, but should be
   // ready to provide a compensating write barrier as necessary
   // if that storage came out of a non-young region. The efficiency
   // of this implementation depends crucially on being able to
   // answer very efficiently in constant time whether a piece of
   // storage in the heap comes from a young region or not.
   // See ReduceInitialCardMarks.
   virtual bool can_elide_tlab_store_barriers() const {
     // 6920090: Temporarily disabled, because of lingering
     // instabilities related to RICM with G1. In the
     // interim, the option ReduceInitialCardMarksForG1
     // below is left solely as a debugging device at least
     // until 6920109 fixes the instabilities.
     return ReduceInitialCardMarksForG1;
   }
   virtual bool card_mark_must_follow_store() const {
     return true;
   }
   bool is_in_young(oop obj) {
     HeapRegion* hr = heap_region_containing(obj);
     return hr != NULL && hr->is_young();
   }
   // We don't need barriers for initializing stores to objects
   // in the young gen: for the SATB pre-barrier, there is no
   // pre-value that needs to be remembered; for the remembered-set
   // update logging post-barrier, we don't maintain remembered set
   // information for young gen objects. Note that non-generational
   // G1 does not have any "young" objects, should not elide
   // the rs logging barrier and so should always answer false below.
   // However, non-generational G1 (-XX:-G1Gen) appears to have
   // bit-rotted so was not tested below.
   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
     // Re 6920090, 6920109 above.
     assert(ReduceInitialCardMarksForG1, "Else cannot be here");
     assert(G1Gen || !is_in_young(new_obj),
            "Non-generational G1 should never return true below");
     return is_in_young(new_obj);
   }
   // Can a compiler elide a store barrier when it writes
   // a permanent oop into the heap?  Applies when the compiler
   // is storing x to the heap, where x->is_perm() is true.
   virtual bool can_elide_permanent_oop_store_barriers() const {
     // At least until perm gen collection is also G1-ified, at
     // which point this should return false.
     return true;
   }
   virtual bool allocs_are_zero_filled();
   // The boundary between a "large" and "small" array of primitives, in
   // words.
   virtual size_t large_typearray_limit();
   // Returns "true" iff the given word_size is "very large".
   static bool isHumongous(size_t word_size) {
     // Note this has to be strictly greater-than as the TLABs
     // are capped at the humongous thresold and we want to
     // ensure that we don't try to allocate a TLAB as
     // humongous and that we don't allocate a humongous
     // object in a TLAB.
     return word_size > _humongous_object_threshold_in_words;
   }
   // Update mod union table with the set of dirty cards.
   void updateModUnion();
   // Set the mod union bits corresponding to the given memRegion.  Note
   // that this is always a safe operation, since it doesn't clear any
   // bits.
   void markModUnionRange(MemRegion mr);
   // Records the fact that a marking phase is no longer in progress.
   void set_marking_complete() {
     _mark_in_progress = false;
   }
   void set_marking_started() {
     _mark_in_progress = true;
   }
   bool mark_in_progress() {
     return _mark_in_progress;
   }
   // Print the maximum heap capacity.
   virtual size_t max_capacity() const;
   virtual jlong millis_since_last_gc();
   // Perform any cleanup actions necessary before allowing a verification.
   virtual void prepare_for_verify();
   // Perform verification.
   // use_prev_marking == true  -> use "prev" marking information,
   // use_prev_marking == false -> use "next" marking information
   // NOTE: Only the "prev" marking information is guaranteed to be
   // consistent most of the time, so most calls to this should use
   // use_prev_marking == true. Currently, there is only one case where
   // this is called with use_prev_marking == false, which is to verify
   // the "next" marking information at the end of remark.
   void verify(bool allow_dirty, bool silent, bool use_prev_marking);
   // Override; it uses the "prev" marking information
   virtual void verify(bool allow_dirty, bool silent);
   // Default behavior by calling print(tty);
   virtual void print() const;
   // This calls print_on(st, PrintHeapAtGCExtended).
   virtual void print_on(outputStream* st) const;
   // If extended is true, it will print out information for all
   // regions in the heap by calling print_on_extended(st).
   virtual void print_on(outputStream* st, bool extended) const;
   virtual void print_on_extended(outputStream* st) const;
   virtual void print_gc_threads_on(outputStream* st) const;
   virtual void gc_threads_do(ThreadClosure* tc) const;
   // Override
   void print_tracing_info() const;
   // If "addr" is a pointer into the (reserved?) heap, returns a positive
   // number indicating the "arena" within the heap in which "addr" falls.
   // Or else returns 0.
   virtual int addr_to_arena_id(void* addr) const;
   // Convenience function to be used in situations where the heap type can be
   // asserted to be this type.
   static G1CollectedHeap* heap();
   void empty_young_list();
   bool should_set_young_locked();
   void set_region_short_lived_locked(HeapRegion* hr);
   // add appropriate methods for any other surv rate groups
   YoungList* young_list() { return _young_list; }
   // debugging
   bool check_young_list_well_formed() {
     return _young_list->check_list_well_formed();
   }
   bool check_young_list_empty(bool check_heap,
                               bool check_sample = true);
   // *** Stuff related to concurrent marking.  It's not clear to me that so
   // many of these need to be public.
   // The functions below are helper functions that a subclass of
   // "CollectedHeap" can use in the implementation of its virtual
   // functions.
   // This performs a concurrent marking of the live objects in a
   // bitmap off to the side.
   void doConcurrentMark();
   // This is called from the marksweep collector which then does
   // a concurrent mark and verifies that the results agree with
   // the stop the world marking.
   void checkConcurrentMark();
   void do_sync_mark();
   bool isMarkedPrev(oop obj) const;
   bool isMarkedNext(oop obj) const;
   // use_prev_marking == true  -> use "prev" marking information,
   // use_prev_marking == false -> use "next" marking information
   bool is_obj_dead_cond(const oop obj,
                         const HeapRegion* hr,
                         const bool use_prev_marking) const {
     if (use_prev_marking) {
       return is_obj_dead(obj, hr);
     } else {
       return is_obj_ill(obj, hr);
     }
   }
   // Determine if an object is dead, given the object and also
   // the region to which the object belongs. An object is dead
   // iff a) it was not allocated since the last mark and b) it
   // is not marked.
   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
     return
       !hr->obj_allocated_since_prev_marking(obj) &&
       !isMarkedPrev(obj);
   }
   // This is used when copying an object to survivor space.
   // If the object is marked live, then we mark the copy live.
   // If the object is allocated since the start of this mark
   // cycle, then we mark the copy live.
   // If the object has been around since the previous mark
   // phase, and hasn't been marked yet during this phase,
   // then we don't mark it, we just wait for the
   // current marking cycle to get to it.
   // This function returns true when an object has been
   // around since the previous marking and hasn't yet
   // been marked during this marking.
   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
     return
       !hr->obj_allocated_since_next_marking(obj) &&
       !isMarkedNext(obj);
   }
   // Determine if an object is dead, given only the object itself.
   // This will find the region to which the object belongs and
   // then call the region version of the same function.
   // Added if it is in permanent gen it isn't dead.
   // Added if it is NULL it isn't dead.
   // use_prev_marking == true  -> use "prev" marking information,
   // use_prev_marking == false -> use "next" marking information
   bool is_obj_dead_cond(const oop obj,
                         const bool use_prev_marking) {
     if (use_prev_marking) {
       return is_obj_dead(obj);
     } else {
       return is_obj_ill(obj);
     }
   }
   bool is_obj_dead(const oop obj) {
     const HeapRegion* hr = heap_region_containing(obj);
     if (hr == NULL) {
       if (Universe::heap()->is_in_permanent(obj))
         return false;
       else if (obj == NULL) return false;
       else return true;
     }
     else return is_obj_dead(obj, hr);
   }
   bool is_obj_ill(const oop obj) {
     const HeapRegion* hr = heap_region_containing(obj);
     if (hr == NULL) {
       if (Universe::heap()->is_in_permanent(obj))
         return false;
       else if (obj == NULL) return false;
       else return true;
     }
     else return is_obj_ill(obj, hr);
   }
   // The following is just to alert the verification code
   // that a full collection has occurred and that the
   // remembered sets are no longer up to date.
   bool _full_collection;
   void set_full_collection() { _full_collection = true;}
   void clear_full_collection() {_full_collection = false;}
   bool full_collection() {return _full_collection;}
   ConcurrentMark* concurrent_mark() const { return _cm; }
   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
   // The dirty cards region list is used to record a subset of regions
   // whose cards need clearing. The list if populated during the
   // remembered set scanning and drained during the card table
   // cleanup. Although the methods are reentrant, population/draining
   // phases must not overlap. For synchronization purposes the last
   // element on the list points to itself.
   HeapRegion* _dirty_cards_region_list;
   void push_dirty_cards_region(HeapRegion* hr);
   HeapRegion* pop_dirty_cards_region();
 public:
   void stop_conc_gc_threads();
   // <NEW PREDICTION>
   double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
   void check_if_region_is_too_expensive(double predicted_time_ms);
   size_t pending_card_num();
   size_t max_pending_card_num();
   size_t cards_scanned();
   // </NEW PREDICTION>
 protected:
   size_t _max_heap_capacity;
 //  debug_only(static void check_for_valid_allocation_state();)
 public:
   // Temporary: call to mark things unimplemented for the G1 heap (e.g.,
   // MemoryService).  In productization, we can make this assert false
   // to catch such places (as well as searching for calls to this...)
   static void g1_unimplemented();
 };
 #define use_local_bitmaps         1
 #define verify_local_bitmaps      0
 #define oop_buffer_length       256
 #ifndef PRODUCT
 class GCLabBitMap;
 class GCLabBitMapClosure: public BitMapClosure {
 private:
   ConcurrentMark* _cm;
   GCLabBitMap*    _bitmap;
 public:
   GCLabBitMapClosure(ConcurrentMark* cm,
                      GCLabBitMap* bitmap) {
     _cm     = cm;
     _bitmap = bitmap;
   }
   virtual bool do_bit(size_t offset);
 };
 #endif // !PRODUCT
 class GCLabBitMap: public BitMap {
 private:
   ConcurrentMark* _cm;
   int       _shifter;
   size_t    _bitmap_word_covers_words;
   // beginning of the heap
   HeapWord* _heap_start;
   // this is the actual start of the GCLab
   HeapWord* _real_start_word;
   // this is the actual end of the GCLab
   HeapWord* _real_end_word;
   // this is the first word, possibly located before the actual start
   // of the GCLab, that corresponds to the first bit of the bitmap
   HeapWord* _start_word;
   // size of a GCLab in words
   size_t _gclab_word_size;
   static int shifter() {
     return MinObjAlignment - 1;
   }
   // how many heap words does a single bitmap word corresponds to?
   static size_t bitmap_word_covers_words() {
     return BitsPerWord << shifter();
   }
   size_t gclab_word_size() const {
     return _gclab_word_size;
   }
   // Calculates actual GCLab size in words
   size_t gclab_real_word_size() const {
     return bitmap_size_in_bits(pointer_delta(_real_end_word, _start_word))
            / BitsPerWord;
   }
   static size_t bitmap_size_in_bits(size_t gclab_word_size) {
     size_t bits_in_bitmap = gclab_word_size >> shifter();
     // We are going to ensure that the beginning of a word in this
     // bitmap also corresponds to the beginning of a word in the
     // global marking bitmap. To handle the case where a GCLab
     // starts from the middle of the bitmap, we need to add enough
     // space (i.e. up to a bitmap word) to ensure that we have
     // enough bits in the bitmap.
     return bits_in_bitmap + BitsPerWord - 1;
   }
 public:
   GCLabBitMap(HeapWord* heap_start, size_t gclab_word_size)
     : BitMap(bitmap_size_in_bits(gclab_word_size)),
       _cm(G1CollectedHeap::heap()->concurrent_mark()),
       _shifter(shifter()),
       _bitmap_word_covers_words(bitmap_word_covers_words()),
       _heap_start(heap_start),
       _gclab_word_size(gclab_word_size),
       _real_start_word(NULL),
       _real_end_word(NULL),
       _start_word(NULL)
   {
     guarantee( size_in_words() >= bitmap_size_in_words(),
                "just making sure");
   }
   inline unsigned heapWordToOffset(HeapWord* addr) {
     unsigned offset = (unsigned) pointer_delta(addr, _start_word) >> _shifter;
     assert(offset < size(), "offset should be within bounds");
     return offset;
   }
   inline HeapWord* offsetToHeapWord(size_t offset) {
     HeapWord* addr =  _start_word + (offset << _shifter);
     assert(_real_start_word <= addr && addr < _real_end_word, "invariant");
     return addr;
   }
   bool fields_well_formed() {
     bool ret1 = (_real_start_word == NULL) &&
                 (_real_end_word == NULL) &&
                 (_start_word == NULL);
     if (ret1)
       return true;
     bool ret2 = _real_start_word >= _start_word &&
       _start_word < _real_end_word &&
       (_real_start_word + _gclab_word_size) == _real_end_word &&
       (_start_word + _gclab_word_size + _bitmap_word_covers_words)
                                                               > _real_end_word;
     return ret2;
   }
   inline bool mark(HeapWord* addr) {
     guarantee(use_local_bitmaps, "invariant");
     assert(fields_well_formed(), "invariant");
     if (addr >= _real_start_word && addr < _real_end_word) {
       assert(!isMarked(addr), "should not have already been marked");
       // first mark it on the bitmap
       at_put(heapWordToOffset(addr), true);
       return true;
     } else {
       return false;
     }
   }
   inline bool isMarked(HeapWord* addr) {
     guarantee(use_local_bitmaps, "invariant");
     assert(fields_well_formed(), "invariant");
     return at(heapWordToOffset(addr));
   }
   void set_buffer(HeapWord* start) {
     guarantee(use_local_bitmaps, "invariant");
     clear();
     assert(start != NULL, "invariant");
     _real_start_word = start;
     _real_end_word   = start + _gclab_word_size;
     size_t diff =
       pointer_delta(start, _heap_start) % _bitmap_word_covers_words;
     _start_word = start - diff;
     assert(fields_well_formed(), "invariant");
   }
 #ifndef PRODUCT
   void verify() {
     // verify that the marks have been propagated
     GCLabBitMapClosure cl(_cm, this);
     iterate(&cl);
   }
 #endif // PRODUCT
   void retire() {
     guarantee(use_local_bitmaps, "invariant");
     assert(fields_well_formed(), "invariant");
     if (_start_word != NULL) {
       CMBitMap*       mark_bitmap = _cm->nextMarkBitMap();
       // this means that the bitmap was set up for the GCLab
       assert(_real_start_word != NULL && _real_end_word != NULL, "invariant");
       mark_bitmap->mostly_disjoint_range_union(this,
 , // always start from the start of the bitmap
                                 _start_word,
                                 gclab_real_word_size());
       _cm->grayRegionIfNecessary(MemRegion(_real_start_word, _real_end_word));
 #ifndef PRODUCT
       if (use_local_bitmaps && verify_local_bitmaps)
         verify();
 #endif // PRODUCT
     } else {
       assert(_real_start_word == NULL && _real_end_word == NULL, "invariant");
     }
   }
   size_t bitmap_size_in_words() const {
     return (bitmap_size_in_bits(gclab_word_size()) + BitsPerWord - 1) / BitsPerWord;
   }
 };
 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
 private:
   bool        _retired;
   bool        _during_marking;
   GCLabBitMap _bitmap;
 public:
   G1ParGCAllocBuffer(size_t gclab_word_size) :
     ParGCAllocBuffer(gclab_word_size),
     _during_marking(G1CollectedHeap::heap()->mark_in_progress()),
     _bitmap(G1CollectedHeap::heap()->reserved_region().start(), gclab_word_size),
     _retired(false)
   { }
   inline bool mark(HeapWord* addr) {
     guarantee(use_local_bitmaps, "invariant");
     assert(_during_marking, "invariant");
     return _bitmap.mark(addr);
   }
   inline void set_buf(HeapWord* buf) {
     if (use_local_bitmaps && _during_marking)
       _bitmap.set_buffer(buf);
     ParGCAllocBuffer::set_buf(buf);
     _retired = false;
   }
   inline void retire(bool end_of_gc, bool retain) {
     if (_retired)
       return;
     if (use_local_bitmaps && _during_marking) {
       _bitmap.retire();
     }
     ParGCAllocBuffer::retire(end_of_gc, retain);
     _retired = true;
   }
 };
 class G1ParScanThreadState : public StackObj {
 protected:
   G1CollectedHeap* _g1h;
   RefToScanQueue*  _refs;
   DirtyCardQueue   _dcq;
   CardTableModRefBS* _ct_bs;
   G1RemSet* _g1_rem;
   typedef GrowableArray<StarTask> OverflowQueue;
   OverflowQueue* _overflowed_refs;
   G1ParGCAllocBuffer  _surviving_alloc_buffer;
   G1ParGCAllocBuffer  _tenured_alloc_buffer;
   G1ParGCAllocBuffer* _alloc_buffers[GCAllocPurposeCount];
   ageTable            _age_table;
   size_t           _alloc_buffer_waste;
   size_t           _undo_waste;
   OopsInHeapRegionClosure*      _evac_failure_cl;
   G1ParScanHeapEvacClosure*     _evac_cl;
   G1ParScanPartialArrayClosure* _partial_scan_cl;
   int _hash_seed;
   int _queue_num;
   int _term_attempts;
 #if G1_DETAILED_STATS
   int _pushes, _pops, _steals, _steal_attempts;
   int _overflow_pushes;
 #endif
   double _start;
   double _start_strong_roots;
   double _strong_roots_time;
   double _start_term;
   double _term_time;
   // Map from young-age-index (0 == not young, 1 is youngest) to
   // surviving words. base is what we get back from the malloc call
   size_t* _surviving_young_words_base;
   // this points into the array, as we use the first few entries for padding
   size_t* _surviving_young_words;
 #define PADDING_ELEM_NUM (64 / sizeof(size_t))
   void   add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; }
   void   add_to_undo_waste(size_t waste)         { _undo_waste += waste; }
   DirtyCardQueue& dirty_card_queue()             { return _dcq;  }
   CardTableModRefBS* ctbs()                      { return _ct_bs; }
   template <class T> void immediate_rs_update(HeapRegion* from, T* p, int tid) {
     if (!from->is_survivor()) {
       _g1_rem->par_write_ref(from, p, tid);
     }
   }
   template <class T> void deferred_rs_update(HeapRegion* from, T* p, int tid) {
     // If the new value of the field points to the same region or
     // is the to-space, we don't need to include it in the Rset updates.
     if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) {
       size_t card_index = ctbs()->index_for(p);
       // If the card hasn't been added to the buffer, do it.
       if (ctbs()->mark_card_deferred(card_index)) {
         dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index));
       }
     }
   }
 public:
   G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num);
   ~G1ParScanThreadState() {
     FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
   }
   RefToScanQueue*   refs()            { return _refs;             }
   OverflowQueue*    overflowed_refs() { return _overflowed_refs;  }
   ageTable*         age_table()       { return &_age_table;       }
   G1ParGCAllocBuffer* alloc_buffer(GCAllocPurpose purpose) {
     return _alloc_buffers[purpose];
   }
   size_t alloc_buffer_waste()                    { return _alloc_buffer_waste; }
   size_t undo_waste()                            { return _undo_waste; }
   template <class T> void push_on_queue(T* ref) {
     assert(ref != NULL, "invariant");
     assert(has_partial_array_mask(ref) ||
            _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(ref)), "invariant");
 #ifdef ASSERT
     if (has_partial_array_mask(ref)) {
       oop p = clear_partial_array_mask(ref);
       // Verify that we point into the CS
       assert(_g1h->obj_in_cs(p), "Should be in CS");
     }
 #endif
     if (!refs()->push(ref)) {
       overflowed_refs()->push(ref);
       IF_G1_DETAILED_STATS(note_overflow_push());
     } else {
       IF_G1_DETAILED_STATS(note_push());
     }
   }
   void pop_from_queue(StarTask& ref) {
     if (refs()->pop_local(ref)) {
       assert((oop*)ref != NULL, "pop_local() returned true");
       assert(UseCompressedOops || !ref.is_narrow(), "Error");
       assert(has_partial_array_mask((oop*)ref) ||
              _g1h->is_in_g1_reserved(ref.is_narrow() ? oopDesc::load_decode_heap_oop((narrowOop*)ref)
                                                      : oopDesc::load_decode_heap_oop((oop*)ref)),
               "invariant");
       IF_G1_DETAILED_STATS(note_pop());
     } else {
       StarTask null_task;
       ref = null_task;
     }
   }
   void pop_from_overflow_queue(StarTask& ref) {
     StarTask new_ref = overflowed_refs()->pop();
     assert((oop*)new_ref != NULL, "pop() from a local non-empty stack");
     assert(UseCompressedOops || !new_ref.is_narrow(), "Error");
     assert(has_partial_array_mask((oop*)new_ref) ||
            _g1h->is_in_g1_reserved(new_ref.is_narrow() ? oopDesc::load_decode_heap_oop((narrowOop*)new_ref)
                                                        : oopDesc::load_decode_heap_oop((oop*)new_ref)),
            "invariant");
     ref = new_ref;
   }
   int refs_to_scan()                             { return refs()->size();                 }
   int overflowed_refs_to_scan()                  { return overflowed_refs()->length();    }
   template <class T> void update_rs(HeapRegion* from, T* p, int tid) {
     if (G1DeferredRSUpdate) {
       deferred_rs_update(from, p, tid);
     } else {
       immediate_rs_update(from, p, tid);
     }
   }
   HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
     HeapWord* obj = NULL;
     size_t gclab_word_size = _g1h->desired_plab_sz(purpose);
     if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
       G1ParGCAllocBuffer* alloc_buf = alloc_buffer(purpose);
       assert(gclab_word_size == alloc_buf->word_sz(),
              "dynamic resizing is not supported");
       add_to_alloc_buffer_waste(alloc_buf->words_remaining());
       alloc_buf->retire(false, false);
       HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size);
       if (buf == NULL) return NULL; // Let caller handle allocation failure.
       // Otherwise.
       alloc_buf->set_buf(buf);
       obj = alloc_buf->allocate(word_sz);
       assert(obj != NULL, "buffer was definitely big enough...");
     } else {
       obj = _g1h->par_allocate_during_gc(purpose, word_sz);
     }
     return obj;
   }
   HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) {
     HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
     if (obj != NULL) return obj;
     return allocate_slow(purpose, word_sz);
   }
   void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
     if (alloc_buffer(purpose)->contains(obj)) {
       assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
              "should contain whole object");
       alloc_buffer(purpose)->undo_allocation(obj, word_sz);
     } else {
       CollectedHeap::fill_with_object(obj, word_sz);
       add_to_undo_waste(word_sz);
     }
   }
   void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) {
     _evac_failure_cl = evac_failure_cl;
   }
   OopsInHeapRegionClosure* evac_failure_closure() {
     return _evac_failure_cl;
   }
   void set_evac_closure(G1ParScanHeapEvacClosure* evac_cl) {
     _evac_cl = evac_cl;
   }
   void set_partial_scan_closure(G1ParScanPartialArrayClosure* partial_scan_cl) {
     _partial_scan_cl = partial_scan_cl;
   }
   int* hash_seed() { return &_hash_seed; }
   int  queue_num() { return _queue_num; }
   int term_attempts()   { return _term_attempts; }
   void note_term_attempt()  { _term_attempts++; }
 #if G1_DETAILED_STATS
   int pushes()          { return _pushes; }
   int pops()            { return _pops; }
   int steals()          { return _steals; }
   int steal_attempts()  { return _steal_attempts; }
   int overflow_pushes() { return _overflow_pushes; }
   void note_push()          { _pushes++; }
   void note_pop()           { _pops++; }
   void note_steal()         { _steals++; }
   void note_steal_attempt() { _steal_attempts++; }
   void note_overflow_push() { _overflow_pushes++; }
 #endif
   void start_strong_roots() {
     _start_strong_roots = os::elapsedTime();
   }
   void end_strong_roots() {
     _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
   }
   double strong_roots_time() { return _strong_roots_time; }
   void start_term_time() {
     note_term_attempt();
     _start_term = os::elapsedTime();
   }
   void end_term_time() {
     _term_time += (os::elapsedTime() - _start_term);
   }
   double term_time() { return _term_time; }
   double elapsed() {
     return os::elapsedTime() - _start;
   }
   size_t* surviving_young_words() {
     // We add on to hide entry 0 which accumulates surviving words for
     // age -1 regions (i.e. non-young ones)
     return _surviving_young_words;
   }
   void retire_alloc_buffers() {
     for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
       size_t waste = _alloc_buffers[ap]->words_remaining();
       add_to_alloc_buffer_waste(waste);
       _alloc_buffers[ap]->retire(true, false);
     }
   }
 private:
   template <class T> void deal_with_reference(T* ref_to_scan) {
     if (has_partial_array_mask(ref_to_scan)) {
       _partial_scan_cl->do_oop_nv(ref_to_scan);
     } else {
       // Note: we can use "raw" versions of "region_containing" because
       // "obj_to_scan" is definitely in the heap, and is not in a
       // humongous region.
       HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan);
       _evac_cl->set_region(r);
       _evac_cl->do_oop_nv(ref_to_scan);
     }
   }
 public:
   void trim_queue() {
     // I've replicated the loop twice, first to drain the overflow
     // queue, second to drain the task queue. This is better than
     // having a single loop, which checks both conditions and, inside
     // it, either pops the overflow queue or the task queue, as each
     // loop is tighter. Also, the decision to drain the overflow queue
     // first is not arbitrary, as the overflow queue is not visible
     // to the other workers, whereas the task queue is. So, we want to
     // drain the "invisible" entries first, while allowing the other
     // workers to potentially steal the "visible" entries.
     while (refs_to_scan() > 0 || overflowed_refs_to_scan() > 0) {
       while (overflowed_refs_to_scan() > 0) {
         StarTask ref_to_scan;
         assert((oop*)ref_to_scan == NULL, "Constructed above");
         pop_from_overflow_queue(ref_to_scan);
         // We shouldn't have pushed it on the queue if it was not
         // pointing into the CSet.
         assert((oop*)ref_to_scan != NULL, "Follows from inner loop invariant");
         if (ref_to_scan.is_narrow()) {
           assert(UseCompressedOops, "Error");
           narrowOop* p = (narrowOop*)ref_to_scan;
           assert(!has_partial_array_mask(p) &&
                  _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(p)), "sanity");
           deal_with_reference(p);
         } else {
           oop* p = (oop*)ref_to_scan;
           assert((has_partial_array_mask(p) && _g1h->is_in_g1_reserved(clear_partial_array_mask(p))) ||
                  _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(p)), "sanity");
           deal_with_reference(p);
         }
       }
       while (refs_to_scan() > 0) {
         StarTask ref_to_scan;
         assert((oop*)ref_to_scan == NULL, "Constructed above");
         pop_from_queue(ref_to_scan);
         if ((oop*)ref_to_scan != NULL) {
           if (ref_to_scan.is_narrow()) {
             assert(UseCompressedOops, "Error");
             narrowOop* p = (narrowOop*)ref_to_scan;
             assert(!has_partial_array_mask(p) &&
                     _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(p)), "sanity");
             deal_with_reference(p);
           } else {
             oop* p = (oop*)ref_to_scan;
             assert((has_partial_array_mask(p) && _g1h->obj_in_cs(clear_partial_array_mask(p))) ||
                    _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(p)), "sanity");
             deal_with_reference(p);
           }
         }
       }
     }
   }
 };

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp@b9bc732be7c0 (annotated)

src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp